Ben
Benjamin "Ben" Tennyson is the grandson of Max Tennyson, friend to his former enemy Kevin and twin cousin of Gwen Tennyson. He is the only person in the world to be able to use the Omnitrix, an alien device that allows him to transform into any various 10 aliens found across the galaxy, hence the name "Ben 10." Ben eventually aquires new aliens through unlocking them in the Omnitrix and absorbing DNA along with the loss of Ghostfreak. Whose home planet are in an alliance with Planet Fusion. In Ben 10: Alien Force, Ben is five years older and his Omnitrix has been recalibrated, allowing access to 10 new alien forms, at the cost of losing his original aliens from the first series. After the first Terrafusers landed on earth, 10 year old Ben (as Fourarms) teamed up with Dexter to defend Foster's Home, Mac, and Bloo from the Fusion Spawn invaders. With the help of Professor Utonium, Dexter developed plans for a Electronic Pulse Cannon to disable the Terrafusers. Unfortunately, two key parts to the EPC were in the custody of both his nemesis, Mandark, and the villain, Mojo Jojo. Mojo's lair was raided by a team consisting of Ben, Numbuh Two, Bubbles, and Blossom. Ben was able to bypass Mojo's security system as the Galvanic Mechomorph he called "Upgrade." Despite a Fusion Spawn attack, that part was recovered without a hitch, since Mojo and his minions had abandoned the lair in their attempt to conquer Planet Fusion. Ben (once again as Fourarms) then helped defend Dexter's ship against the Fusion Spawns in order to buy him and Professor Utonium time to fire the cannon. However, due to a miscalculation by Mandark, the cannon fire was too late to stop the Terafusers from summoning Planet Fusion and its army to Earth. In the Future, Ben and Numbuh Five help the Hero against a Fusion Spawn attack, and bring him/her up to speed on the status of the invasion. He is presumably lost in the fall of Tech Square (The Future) as he is one of the holograms in Hero Square. In the past, Ben is in the Offworld Plaza, serving as one of the four guides players can choose to work for. He is constantly lending a hand in the fight against Fuse and his minions, whether he is fighting, helping his Grandpa Max create his satellite to survey Planet Fusion, or cleaning up the Space Port in order to take the war directly to the Planet. Ben is having more problems than usual with the Omnitrix, which started acting strange as soon as Planet Fusion appeared. When Ben is able to use the Omnitrix, Fusion Gwen always appears to steal a piece from his alien hero forms, such as a talon from Jetray, fur from Spidermonkey, a stone from Chromastone, or a swamp root from Swampfire, presumably in order to create Fusions of them. Later it was shown he had also stolen a scale from Humongousar, and had earlier aquirred a barbell from Fourarms. His Omnitrix has been allowing him to turn into more of his aliens recently, such as Echo Echo and Alien X. To better combat the invasion, Ben has made uneasy alliances with his mortal nemesis, Vilgax, and Gwen's mortal enemy, Hex. More recently, he has been forced to come to terms with Albedo, who has joined the war against Fuse. Also, his Pyronite friend Alan, and his girlfriend's Galvanic Mechomorph pet, Ship, have come to help out with the war as well. Ben is unique as he is the only guide without a nano of himself, but he has three nanos of his aliens (Four including Alien X) thus he has the most nanos of himself. Also a hidden nano of his younger self was found in the game files, as well as of Upgrade and Ghostfreak, hinting that in the future he will have yet more nanos based on him and/or his other forms. Interestingly, all of his alien forms are Cosmix. Also he is the only non generic character to have a pallette swapped version of him.